Thermostatic instrument



July 7, 1925. 1,544,549

5. G. BARNETT THERMOSTATIC INSTRUMENT Filed April 14, 1922 Snowdonthermostat functioned. whole value in protection from fire is in theability tem to operate its alarm while`the lire is in4 Patented July 7,1925. .l

STOCKTON G.v BABNETT, 0F NEW YORK, N. Y.

mmos'rarxc :Nsrnuxnu'n' Application led April 14,1822.A Serial No.552,687.

To all wlwm 'it may com-em:

Be it known that I, S'rooKToN G. BARNn'rr, 'a citizen of the UnitedStates, residin at No. 63 Morningside Avenue, New ork, county and Stateof New York, have vented certain new and useful Improvements inThermostatic Instruments; and I do hereby declare the following to be afull, clear, and exact description ofthe invention, such as will enableothers skilled in the art to which it' appertains to make and use thesame.

This invention relates to thermostats, and more particularly to'improvements in compensating thermostats useful in detecting rapidtemperature variations.

Primarily, the object is to produce apparatus generally useful in firealarm systems, and useful even in fire extinguishing or sprinklersystems; and more particularlyit is an object to produce a compensatingtemperature detector which uniformly functions to sound a fire alarm inall temperatures whether warm or cold, and which similarly appropriatelyfunctions to sound an alarm even though the daily or seasonable weathertemperature conditions may rapidlychange.

It is common practice to use a bimetallic heat sensitive element,commonly known as a thermostatic bar, to perform a variety of purposes,as for example to detect a temperature change; and this was acomparativel simple undertaking where it was soug 1t only to detect orcatch any predetermined lixed point of temperature because thethermostatic bar deflected as the temperature increased and broke ormade contact on an electrical alarm or signal circuit. The developmentof this art was quickly impeded as it was conceived, due to theunfailing capacity of the thermostat to untimely produce false signalsor alarms when subjected to seasonal increases in temperature, orothercomparatively slow temperature increases due to industrial conditions orheating systems. By adjusting the thermostat to operate at a hi h temerature, this diiiculty was overcome, ut 'suc adjustment introduced afatal delay as to actual fires, because the fire gained headway beforethe Practically thedamage by of a lire device or sysf its incipientstage; and my mostat erforms this object.

On t e other hand, fixed temperature thermostats, askn'own in the art,when set to give a quick alarm offire so as to detect the fire in itsinci ient stage, will necessarily give false a arms and particularly sowhen the thermostat and alarm system is used in the wintertime inunheated buildings, for in such a situation there necessarily arisesseasonable and weather temperature changes to which the old fixed typethermostat cannot adapt itself, with the result that when suchseasonable temperature changes occur the alarm prematurely sounds. Theold devices thus have characteristics. which make them either too slowto be eiicient or too fast for service, and therefore, presentlyknown'thermostats are so erratic that they are not useful in fire alarmsystems.

Inventors anduengineers have long sought to so construct `and combinethermostatic parts as will-cause the device to quickly produce an alarmor signal upon sudden tempcrature variations, such as are caused byvfire; and which at the same time will dependably follow-up daily andseasonable temperature and Weather fluctuations yet steadfastly remaininert, with'out alarming; and to accomplish this purpose is to provide asuccessful fire thermostatic detector capable of valuable use in lirealarm systems, and until such is attained thermostats cannot besuccessfully used in fire control and alarm systems.

It was known that a compensating thermostat would be useful in this newfield of endeavor; and by thermostatic compensation is meant the-abilityof a thermostat to move up or down, follow-up so to speak, all slowtemperature changes, known as weather or seasonal changes, withoutopening or closing a circuit, where at the same time it will produce analarm if a quick temperature change occurs. Engineers and inventorsimproved therhave, it appears, correct theoretical knowledge of whatapparatus is needed to carr out the purposes in View, but however sucphysical apparatus has not been forthcoming, because noone as yet hasproduced a thermostat which""will adapt itself to weather and seasontemperature fluctuations without at the same time producing a falsealarm,

and which will, conversely,.produce an alarm without compensating.AApparatus has of course been produced and tried, but found ,missinginthe one particular if sucient in the other.` y A The object of myinvention isv to pro- ,duce a compensating thermostatic circuit closeror a temperature detector which ernbodies such'improvements in' design,ar-

rangement, and construction of parts as will enable it to dependablycompensate and follow-up all daily, weather, and seasonable temperature'changes, and at the same time of the irst'named thermostatic bar.

y circ'uit closer or temperature detectorwhich employs thermostatic barsof unequal sizes, but'- nevertheless will dependably compensate andactually perform that desirable purpose which others have sought toaccom- The laccompanyin drawings illustrate one embodiment of'g minvention, and though there is describedya preferred form ofconstruction and arrangement of. parts, l claim the right of protectionas to such changes as obviously come within the scope of my invention.v

ln the drawings, plan view ofthe compensating thermostatic temperaturedetector; and Figure 2 shows a side view thereof.

Referrin nowinore particularly to the drawings or'a detailed descriptionof the invention there is shown a post 4 made ofv insulating materialsupported on a base 5; and the base has terminal posts 6 by which thisinstrument is 'connected into an electrical fire alarm or sprinklercircuit.

A spirally formed thermostatc element 48 has its inner end anchored tothe post and its outer .free end left unobstructed toV travelsubstantially concentric to the post;

and another thermostatic'element 9 has one end anchored to the post andits other end arranged movable near the free extrcnity D6 'of the bars,in this instance 8, has a down turned end so as to bring its contactpart 10 in alignment with the contacthead 11 of the ot er bar, and. inthis arrangement the contact points 10 and 11 are arranged in closerelation. Each binding post 6 is.Y

connected through awire or barl l2l with the respective thermostaticparts so that the instrument can be connected into an elec- -triccircuit and' act as a switch to hold said circuit open during the timethe con- 'capacity Figure l illustrates a tact points it) and v11` areheld in spaced v. E deflect equally'inurate of travel d -An importantfeatureA of this invention resides in the definite size andlredetermined relation existing between linear dimension and thethickness dimension of the two parts where the breadth of the partspreferably remain constant.

The two heat sensitive elements 8 and 9 are constructed of bimetallicstock equal in breadth or width. But, however, the element V8, being thelonger one, is made of heavier .material', that is to say, it ismade ofstock somewhat thicker' in-cross section than the part 9.l The fact thatthe longer part is made of heavier stock or vmaterial gives it thecharacteristic of slowly acquiring the temperature of the surroundingatmosphere, and consequently this bar acts -and deflectscomparativelyslowly movement.

- '.lhey thermostaticrbar 9,-being shorter in length thanv the otherbar, is made comparatively light in cross section, and is much thinnerthan the other bar; and thisy construction rovides the shorter bar witha or very rapidly attaining the temperature of the surrounding'medium ofair which causes it to be quickly eected by quick 'temperature changessuch as would be caused by lire thereby causing the bar 9 to rapidlydeiect when subjected to the quick temperaturevariations.

It is desirable to make one bar of heavier stockV than the other inorder that when the temperature quickly rises due to a fire, the quickacting element 9 may move its oth the head 11I awa from the point 10 onthe bar i 8 and there y open the circuit, orit Yis readily seen that incase both bars were made of light material, they would both deflect withthe same celerity, and the pur pose of this instrument would be`defeated. Then again, it is found, when a gradual temperature -variation`such as may occur from day to day in season, that a light and heavythermostaticbar will gradually, at about the same rate ofabsorption,attain rounding atmosphere so that both bars will .or acquirethe same temperature as the sur-v be stimulated 'and become equallyactive atsubstantially the same time when effected by this gradualtemperature change. VThis -last described characteristic is necessary ifthe instrument 1sl to be successful, because possessed of thischaracteristic, the instrumentvwill compensate, follow-up, or adjustitself to the slow temperature variations, and at the same timewill noterratically open the circuit, or, in case of open circuit circl'iit.l i.

Now inasmuch as it is found necry to make one of'the'hars of thin lightstock in instruments, vvwill, not 'erratically close the 1 order todetect fires as above described, and

.inasmuch asf it is essential that the two' liars l.. .-l 4f l and ifthe said long bar 8 is made consid-- erably thicker than the said thinbar 9, that the resulting performance of the instrument, as respectsslowgradual temperature changes, is of such character that both contactpoints 10 and 11 travel at substantially the same rate of speedfandthrough substantially-the same distance for unit slow grad-I ualtemperature variations.

In the actual construction of this compensating thermostat and in orderto enable one to practice the invention, I make, in

some types of the device, one part substantially six inches (6) long andfifty thousandths inches (.050) thick; and for 'the other part, I makeitone and eight tenths inches (1.8) long and fifteen thousandths inches(.015 thick, or some such ap ropriate length and thickness as will earequivalent ratio to these figures.

It is also to be noted that the accompanyingl drawings show a closedcircuit instrument, but an open circuit instrument can just assuccessfully be produced by following the plan of my invention.

Therefore an instrument built in accordance with the plans of thisinvention is capable of quickly detecting fire tem erature, and inaddition thereto, is capab e of compensating or following-up the gradualdaily. or seasonable temperature variations without causing the circuitto sound an alarm.

Having thus described the invention, what I claim is:

l. A compensating thermostat comprising two bimetallic4 heat sensitive,parts adapted to open or close acircuit by deflection, the parts havingsubstantially an unequal len h ratio of six inches (6 to one and eigttenth inches (1.8), an having an unequal thickness ratio of fiftythousandths inches (.050) to fifteen 'thousandths (.015) whereby botharts deflect substantially equally when in u enced by slow temperaturevariations and unequally when influenced by sudden temperature rises,and electrical contacts operated by the parts.

2. A compensatin thermostatic quick change temperature etectorcomprising biinches metallic heat sensitive elements having unequallength ratio and unequal thickness ratio, contact points carriedthereon7 said ratios causing the rate of travel of the longer elementtol substantially equal 'and compensate to that of the shorter elementwhen subjected to gradual temperature changes thereby renderinginoperative the contacts, said ratios causing the rate of travel of theshorter one to be more rapid than' the longer one when subjected to arapid temperature variation thereby rendering the contacts operable. l

3. A compensating thermostat quick change temperature detector having along spiral bimetallic part, a contact head made on the end thereof, ashort spiral bimetallic part, a contact head on the end thereof, saidlong and short s irals being disposed in parallel planes, sai longspiral made of thicker stock than short spiral whereby it compensates toand attains the same rate of travel as the short spiral when a slowgradual temperature variation occurs and does not when a quicktemperature variation occurs.

4. A compensating thermostat quick change detector comprising heatsensitive bimetallic parts, contacts carried thereon, the comparativestructure of the bimetallic parts being such that one part is made of.light Weight thin stock to impart thereto a high rate of tem ratureabsorption to cause this part to quickly deflect at high speed whensubjected to quick temperature changes thus operating the contacts, andsaid light weight thin part being constructed relativelyv short inlength to cause itl to substantially equal and compensate in speed tovthat of the other part whensubjected to slow temperature variationsthereby not operating aforesaid contacts, the said other bimetallic partbeing constructed of thick heavy stock toimpart thereto a slow rate oftemperature absorption whereby it lagsv or deflects slowly in speed whensubjected to quick temperature changes thus contributing to theaforesaid operation of the contacts, said thick heavy part being made ofsubstantial length to enable itto deflect equally in speed to that ofthefirst named part when sub]ected to slow temperature changes thus aidingin maintaining vthe aforesaid inoperativeness of the contacts. 4 Intestimon whereof I aix my si ature.- SIOCKTON G. BARNITT

